# Spec: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#asset
import base64
import io
import json
import logging
import struct
from collections import namedtuple

import numpy
from PIL import Image
from pyrr import Matrix44, quaternion

import moderngl
import custom_moderngl_window

from custom_moderngl_window.loaders.base import BaseLoader
from custom_moderngl_window.loaders.texture import t2d
from custom_moderngl_window.opengl.vao import VAO
from custom_moderngl_window.meta import SceneDescription, TextureDescription
from custom_moderngl_window.scene import Material, MaterialTexture, Mesh, Node, Scene
from custom_moderngl_window.exceptions import ImproperlyConfigured

logger = logging.getLogger(__name__)

GLTF_MAGIC_HEADER = b"glTF"

# Texture wrap values
REPEAT = 10497
CLAMP_TO_EDGE = 33071
MIRRORED_REPEAT = 33648

# numpy dtype mapping
NP_COMPONENT_DTYPE = {
    5121: numpy.uint8,  # GL_UNSIGNED_BYTE
    5123: numpy.uint16,  # GL_UNSIGNED_SHORT
    5125: numpy.uint32,  # GL_UNSIGNED_INT
    5126: numpy.float32,  # GL_FLOAT
}

ComponentType = namedtuple("ComponentType", ["name", "value", "size"])

COMPONENT_TYPE = {
    5120: ComponentType("BYTE", 5120, 1),
    5121: ComponentType("UNSIGNED_BYTE", 5121, 1),
    5122: ComponentType("SHORT", 5122, 2),
    5123: ComponentType("UNSIGNED_SHORT", 5123, 2),
    5125: ComponentType("UNSIGNED_INT", 5125, 4),
    5126: ComponentType("FLOAT", 5126, 4),
}

# dtype to moderngl buffer format
DTYPE_BUFFER_TYPE = {
    numpy.uint8: "u1",  # GL_UNSIGNED_BYTE
    numpy.uint16: "u2",  # GL_UNSIGNED_SHORT
    numpy.uint32: "u4",  # GL_UNSIGNED_INT
    numpy.float32: "f4",  # GL_FLOAT
}

ACCESSOR_TYPE = {
    "SCALAR": 1,
    "VEC2": 2,
    "VEC3": 3,
    "VEC4": 4,
}


class Loader(BaseLoader):
    """Loader for GLTF 2.0 files"""

    kind = "gltf"
    file_extensions = [
        [".gltf"],
        [".glb"],
    ]
    #: Supported GLTF extensions
    #: https://github.com/KhronosGroup/glTF/tree/master/extensions
    supported_extensions = []

    def __init__(self, meta: SceneDescription):
        """Initialize loading GLTF 2 scene.

        Supported formats:

        - gltf json format with external resources
        - gltf embedded buffers
        - glb Binary format
        """
        super().__init__(meta)
        self.scenes = []
        self.nodes = []
        self.meshes = []
        self.materials = []
        self.images = []
        self.samplers = []
        self.textures = []

        self.path = None
        self.scene = None
        self.gltf = None

    def load(self) -> Scene:
        """Load a GLTF 2 scene including referenced textures.

        Returns:
            Scene: The scene instance
        """
        self.path = self.find_scene(self.meta.path)
        if not self.path:
            raise ImproperlyConfigured("Scene '{}' not found".format(self.meta.path))

        self.scene = Scene(self.path)

        # Load gltf json file
        if self.path.suffix == ".gltf":
            self.load_gltf()

        # Load binary gltf file
        if self.path.suffix == ".glb":
            self.load_glb()

        self.gltf.check_version()
        self.gltf.check_extensions(self.supported_extensions)
        self.load_images()
        self.load_samplers()
        self.load_textures()
        self.load_materials()
        self.load_meshes()
        self.load_nodes()

        self.scene.calc_scene_bbox()
        self.scene.prepare()

        return self.scene

    def load_gltf(self):
        """Loads a gltf json file parsing its contents"""
        with open(str(self.path)) as fd:
            self.gltf = GLTFMeta(self.path, json.load(fd), self.meta)

    def load_glb(self):
        """Loads a binary gltf file parsing its contents"""
        with open(str(self.path), "rb") as fd:
            # Check header
            magic = fd.read(4)
            if magic != GLTF_MAGIC_HEADER:
                raise ValueError(
                    "{} has incorrect header {} != {}".format(
                        self.path, magic, GLTF_MAGIC_HEADER
                    )
                )

            version = struct.unpack("<I", fd.read(4))[0]
            if version != 2:
                raise ValueError(
                    f"{self.path} has unsupported version {version}"
                )

            # Total file size including headers
            _ = struct.unpack("<I", fd.read(4))[0]  # noqa

            # Chunk 0 - json
            chunk_0_length = struct.unpack("<I", fd.read(4))[0]
            chunk_0_type = fd.read(4)
            if chunk_0_type != b"JSON":
                raise ValueError(
                    "Expected JSON chunk, not {} in file {}".format(
                        chunk_0_type, self.path
                    )
                )

            json_meta = fd.read(chunk_0_length).decode()

            # chunk 1 - binary buffer
            chunk_1_length = struct.unpack("<I", fd.read(4))[0]
            chunk_1_type = fd.read(4)
            if chunk_1_type != b"BIN\x00":
                raise ValueError(
                    "Expected BIN chunk, not {} in file {}".format(
                        chunk_1_type, self.path
                    )
                )

            self.gltf = GLTFMeta(
                self.path,
                json.loads(json_meta),
                self.meta,
                binary_buffer=fd.read(chunk_1_length),
            )

    def load_images(self):
        """Load images referenced in gltf metadata"""
        for image in self.gltf.images:
            self.images.append(image.load(self.path.parent))

    def load_samplers(self):
        """Load samplers referenced in gltf metadata"""
        for sampler in self.gltf.samplers:
            # Use a sane default sampler if the sampler data is empty
            # Samplers can simply just be json data: "{}"
            if sampler.minFilter is sampler.magFilter is None:
                self.samplers.append(
                    self.ctx.sampler(
                        filter=(moderngl.LINEAR_MIPMAP_LINEAR, moderngl.LINEAR),
                        repeat_x=False,
                        repeat_y=False,
                        anisotropy=16.0,
                    )
                )
            else:
                self.samplers.append(
                    self.ctx.sampler(
                        filter=(sampler.minFilter, sampler.magFilter),
                        repeat_x=sampler.wrapS in [REPEAT, MIRRORED_REPEAT],
                        repeat_y=sampler.wrapT in [REPEAT, MIRRORED_REPEAT],
                        anisotropy=16.0,
                    )
                )

    def load_textures(self):
        """Load textures referenced in gltf metadata"""
        for texture_meta in self.gltf.textures:
            texture = MaterialTexture()

            if texture_meta.source is not None:
                texture.texture = self.images[texture_meta.source]

            if texture_meta.sampler is not None:
                texture.sampler = self.samplers[texture_meta.sampler]

            self.textures.append(texture)

    def load_meshes(self):
        """Load meshes referenced in gltf metadata"""
        for meta_mesh in self.gltf.meshes:
            # Returns a list of meshes
            meshes = meta_mesh.load(self.materials)
            self.meshes.append(meshes)

            for mesh in meshes:
                self.scene.meshes.append(mesh)

    def load_materials(self):
        """Load materials referenced in gltf metadata"""
        # Create material objects
        for meta_mat in self.gltf.materials:
            mat = Material(meta_mat.name)
            mat.color = meta_mat.baseColorFactor or [1.0, 1.0, 1.0, 1.0]
            mat.double_sided = meta_mat.doubleSided

            if meta_mat.baseColorTexture is not None:
                mat.mat_texture = self.textures[meta_mat.baseColorTexture["index"]]

            self.materials.append(mat)
            self.scene.materials.append(mat)

    def load_nodes(self):
        """Load nodes referenced in gltf metadata"""
        # Start with root nodes in the scene
        for node_id in self.gltf.scenes[0].nodes:
            node = self.load_node(self.gltf.nodes[node_id])
            self.scene.root_nodes.append(node)

    def load_node(self, meta, parent=None):
        """Load a single node"""
        # Create the node
        node = Node(name=meta.name)
        self.scene.nodes.append(node)

        if meta.matrix is not None:
            node.matrix = Matrix44(value=meta.matrix)

        if meta.mesh is not None:
            # Since we split up meshes with multiple primitives, this can be a list
            # If only one mesh we set it on the node as normal
            if len(self.meshes[meta.mesh]) == 1:
                node.mesh = self.meshes[meta.mesh][0]
            # If multiple meshes we add them as new child node
            elif len(self.meshes[meta.mesh]) > 1:
                for mesh in self.meshes[meta.mesh]:
                    node.add_child(Node(mesh=mesh))

        if meta.camera is not None:
            # FIXME: Use a proper camera class
            node.camera = self.gltf.cameras[meta.camera]

        if parent:
            parent.add_child(node)

        # Follow children
        if meta.has_children:
            for node_id in meta.children:
                self.load_node(self.gltf.nodes[node_id], parent=node)

        return node


class GLTFMeta:
    """Container for gltf metadata"""

    def __init__(self, path, data, meta, binary_buffer=None):
        """
        :param file: GLTF file name loaded
        :param data: Metadata (json loaded)
        :param binary_buffer: Binary buffer when loading glb files
        """
        self.path = path
        self.data = data
        self.meta = meta

        self.asset = GLTFAsset(data["asset"])
        self.materials = (
            [GLTFMaterial(m) for m in data["materials"]]
            if data.get("materials")
            else []
        )
        self.images = (
            [GLTFImage(i) for i in data["images"]] if data.get("images") else []
        )
        self.samplers = (
            [GLTFSampler(s) for s in data["samplers"]] if data.get("samplers") else []
        )
        self.textures = (
            [GLTFTexture(t) for t in data["textures"]] if data.get("textures") else []
        )
        self.scenes = (
            [GLTFScene(s) for s in data["scenes"]] if data.get("scenes") else []
        )
        self.nodes = [GLTFNode(n) for n in data["nodes"]] if data.get("nodes") else []
        self.meshes = (
            [GLTFMesh(m, self.meta) for m in data["meshes"]]
            if data.get("meshes")
            else []
        )
        self.cameras = (
            [GLTFCamera(c) for c in data["cameras"]] if data.get("cameras") else []
        )
        self.buffer_views = (
            [GLTFBufferView(i, v) for i, v in enumerate(data["bufferViews"])]
            if data.get("bufferViews")
            else []
        )
        self.buffers = (
            [GLTFBuffer(i, b, self.path.parent) for i, b in enumerate(data["buffers"])]
            if data.get("buffers")
            else []
        )
        self.accessors = (
            [GLTFAccessor(i, a) for i, a in enumerate(data["accessors"])]
            if data.get("accessors")
            else []
        )

        # glb files can contain buffer 0 data
        if binary_buffer:
            self.buffers[0].data = binary_buffer

        self._link_data()

        self.buffers_exist()
        self.images_exist()

    def _link_data(self):
        """Add references"""
        # accessors -> buffer_views -> buffers
        for acc in self.accessors:
            acc.bufferView = self.buffer_views[acc.bufferViewId]

        for buffer_view in self.buffer_views:
            buffer_view.buffer = self.buffers[buffer_view.bufferId]

        # Link accessors to mesh primitives
        for mesh in self.meshes:
            for primitive in mesh.primitives:
                if getattr(primitive, "indices", None) is not None:
                    primitive.indices = self.accessors[primitive.indices]
                for name, value in primitive.attributes.items():
                    primitive.attributes[name] = self.accessors[value]

        # Link buffer views to images
        for image in self.images:
            if image.bufferViewId is not None:
                image.bufferView = self.buffer_views[image.bufferViewId]

    @property
    def version(self):
        return self.asset.version

    def check_version(self, required="2.0"):
        if not self.version == required:
            msg = f"GLTF Format version is not 2.0. Version states '{self.version}' in file {self.path}"
            raise ValueError(msg)

    def check_extensions(self, supported):
        """
        "extensionsRequired": ["KHR_draco_mesh_compression"],
        "extensionsUsed": ["KHR_draco_mesh_compression"]
        """
        if self.data.get("extensionsRequired"):
            for ext in self.data.get("extensionsRequired"):
                if ext not in supported:
                    raise ValueError(f"Extension {ext} not supported")

        if self.data.get("extensionsUsed"):
            for ext in self.data.get("extensionsUsed"):
                if ext not in supported:
                    raise ValueError("Extension {ext} not supported")

    def buffers_exist(self):
        """Checks if the bin files referenced exist"""
        for buff in self.buffers:
            if not buff.is_separate_file:
                continue

            path = self.path.parent / buff.uri
            if not path.exists():
                raise FileNotFoundError(
                    "Buffer {} referenced in {} not found".format(path, self.path)
                )

    def images_exist(self):
        """checks if the images references in textures exist"""
        pass


class GLTFAsset:
    """Asset Information"""

    def __init__(self, data):
        self.version = data.get("version")
        self.generator = data.get("generator")
        self.copyright = data.get("copyright")


class GLTFMesh:
    def __init__(self, data: dict, meta: SceneDescription):
        class Primitives:
            def __init__(self, data):
                self.attributes = data.get("attributes")
                self.indices = data.get("indices")
                self.mode = data.get("mode")
                self.material = data.get("material")

        self.meta = meta
        self.name = data.get("name")
        self.primitives = [Primitives(p) for p in data.get("primitives")]

    def load(self, materials):
        name_map = {
            "POSITION": self.meta.attr_names.POSITION,
            "NORMAL": self.meta.attr_names.NORMAL,
            "TEXCOORD_0": self.meta.attr_names.TEXCOORD_0,
            "TANGENT": self.meta.attr_names.TANGENT,
            "JOINTS_0": self.meta.attr_names.JOINTS_0,
            "WEIGHTS_0": self.meta.attr_names.WEIGHTS_0,
            "COLOR_0": self.meta.attr_names.COLOR_0,
        }

        meshes = []

        # Read all primitives as separate meshes for now
        # According to the spec they can have different materials and vertex format
        for primitive in self.primitives:

            vao = VAO(self.name, mode=primitive.mode or moderngl.TRIANGLES)

            # Index buffer
            component_type, index_vbo = self.load_indices(primitive)
            if index_vbo is not None:
                vao.index_buffer(
                    moderngl_window.ctx().buffer(index_vbo.tobytes()),
                    index_element_size=component_type.size,
                )

            attributes = {}
            vbos = self.prepare_attrib_mapping(primitive)

            for vbo_info in vbos:
                dtype, buffer = vbo_info.create()
                vao.buffer(
                    buffer,
                    " ".join(
                        [
                            "{}{}".format(attr[1], DTYPE_BUFFER_TYPE[dtype])
                            for attr in vbo_info.attributes
                        ]
                    ),
                    [name_map[attr[0]] for attr in vbo_info.attributes],
                )

                for attr in vbo_info.attributes:
                    attributes[attr[0]] = {
                        "name": name_map[attr[0]],
                        "components": attr[1],
                        "type": vbo_info.component_type.value,
                    }

            bbox_min, bbox_max = self.get_bbox(primitive)
            meshes.append(
                Mesh(
                    self.name,
                    vao=vao,
                    attributes=attributes,
                    material=materials[primitive.material]
                    if primitive.material is not None
                    else None,
                    bbox_min=bbox_min,
                    bbox_max=bbox_max,
                )
            )

        return meshes

    def load_indices(self, primitive):
        """Loads the index buffer / polygon list for a primitive"""
        if getattr(primitive, "indices") is None:
            return None, None

        _, component_type, buffer = primitive.indices.read()
        return component_type, buffer

    def prepare_attrib_mapping(self, primitive):
        """Pre-parse buffer mappings for each VBO to detect interleaved data for a primitive"""
        buffer_info = []
        for name, accessor in primitive.attributes.items():
            info = VBOInfo(*accessor.info())
            info.attributes.append((name, info.components))

            if buffer_info and buffer_info[-1].buffer_view == info.buffer_view:
                if buffer_info[-1].interleaves(info):
                    buffer_info[-1].merge(info)
                    continue

            buffer_info.append(info)

        return buffer_info

    def get_bbox(self, primitive):
        """Get the bounding box for the mesh"""
        accessor = primitive.attributes.get("POSITION")
        return accessor.min, accessor.max


class VBOInfo:
    """Resolved data about each VBO"""

    def __init__(
        self,
        buffer=None,
        buffer_view=None,
        byte_length=None,
        byte_offset=None,
        component_type=None,
        components=None,
        count=None,
    ):
        self.buffer = buffer  # reference to the buffer
        self.buffer_view = buffer_view
        self.byte_length = byte_length  # Raw byte buffer length
        self.byte_offset = byte_offset  # Raw byte offset
        self.component_type = component_type  # Datatype of each component
        self.components = components
        self.count = count  # number of elements of the component type size

        # list of (name, components) tuples
        self.attributes = []

    def interleaves(self, info):
        """Does the buffer interleave with this one?"""
        return info.byte_offset == self.component_type.size * self.components

    def merge(self, info):
        # NOTE: byte length is the same
        self.components += info.components
        self.attributes += info.attributes

    def create(self):
        """Create the VBO"""
        dtype = NP_COMPONENT_DTYPE[self.component_type.value]
        data = numpy.frombuffer(
            self.buffer.read(
                byte_length=self.byte_length, byte_offset=self.byte_offset
            ),
            count=self.count * self.components,
            dtype=dtype,
        )
        return dtype, data

    def __str__(self):
        return (
            "VBOInfo<buffer={}, buffer_view={},\n"
            "        length={}, offset={}, target={}\n"
            "        component_type={}, components={}, count={}, \n"
            "        attribs={}".format(
                self.buffer.id,
                self.buffer_view.id,
                self.target,
                self.byte_length,
                self.byte_offset,
                self.component_type.value,
                self.components,
                self.count,
                self.attributes,
            )
        )

    def __repr__(self):
        return str(self)


class GLTFAccessor:
    def __init__(self, accessor_id, data):
        self.id = accessor_id
        self.bufferViewId = data.get("bufferView") or 0
        self.bufferView = None
        self.byteOffset = data.get("byteOffset") or 0
        self.componentType = COMPONENT_TYPE[data["componentType"]]
        self.count = data.get("count")
        self.min = numpy.array(data.get("min") or [-0.5, -0.5, -0.5], dtype="f4")
        self.max = numpy.array(data.get("max") or [0.5, 0.5, 0.5], dtype="f4")
        self.type = data.get("type")

    def read(self):
        """
        Reads buffer data
        :return: component count, component type, data
        """
        # ComponentType helps us determine the datatype
        dtype = NP_COMPONENT_DTYPE[self.componentType.value]
        return (
            ACCESSOR_TYPE[self.type],
            self.componentType,
            self.bufferView.read(
                byte_offset=self.byteOffset,
                dtype=dtype,
                count=self.count * ACCESSOR_TYPE[self.type],
            ),
        )

    def info(self):
        """
        Get underlying buffer info for this accessor
        :return: buffer, byte_length, byte_offset, component_type, count
        """
        buffer, byte_length, byte_offset = self.bufferView.info(
            byte_offset=self.byteOffset
        )
        return (
            buffer,
            self.bufferView,
            byte_length,
            byte_offset,
            self.componentType,
            ACCESSOR_TYPE[self.type],
            self.count,
        )


class GLTFBufferView:
    def __init__(self, view_id, data):
        self.id = view_id
        self.bufferId = data.get("buffer")
        self.buffer = None
        self.byteOffset = data.get("byteOffset") or 0
        self.byteLength = data.get("byteLength")
        self.byteStride = data.get("byteStride") or 0
        # Valid: 34962 (ARRAY_BUFFER) and 34963 (ELEMENT_ARRAY_BUFFER) or None

    def read(self, byte_offset=0, dtype=None, count=0):
        data = self.buffer.read(
            byte_offset=byte_offset + self.byteOffset, byte_length=self.byteLength,
        )
        vbo = numpy.frombuffer(data, count=count, dtype=dtype)
        return vbo

    def read_raw(self):
        return self.buffer.read(
            byte_length=self.byteLength, byte_offset=self.byteOffset
        )

    def info(self, byte_offset=0):
        """
        Get the underlying buffer info
        :param byte_offset: byte offset from accessor
        :return: buffer, byte_length, byte_offset
        """
        return self.buffer, self.byteLength, byte_offset + self.byteOffset


class GLTFBuffer:
    def __init__(self, buffer_id, data, path):
        self.id = buffer_id
        self.path = path
        self.byteLength = data.get("byteLength")
        self.uri = data.get("uri")
        self.data = None

    @property
    def has_data_uri(self):
        """Is data embedded in json?"""
        if not self.uri:
            return False

        return self.uri.startswith("data:")

    @property
    def is_separate_file(self):
        """Buffer represents an independent bin file?"""
        return self.uri is not None and not self.has_data_uri

    def open(self):
        if self.data:
            return

        if self.has_data_uri:
            self.data = base64.b64decode(self.uri[self.uri.find(",") + 1:])
            return

        with open(str(self.path / self.uri), "rb") as fd:
            self.data = fd.read()

    def read(self, byte_offset=0, byte_length=0):
        self.open()
        return self.data[byte_offset:byte_offset + byte_length]


class GLTFScene:
    def __init__(self, data):
        self.nodes = data["nodes"]


class GLTFNode:
    def __init__(self, data):
        self.name = data.get("name")
        self.children = data.get("children")
        self.matrix = data.get("matrix")
        self.mesh = data.get("mesh")
        self.camera = data.get("camera")

        self.translation = data.get("translation")
        self.rotation = data.get("rotation")
        self.scale = data.get("scale")

        if self.matrix:
            self.matrix = Matrix44(self.matrix)
        else:
            self.matrix = Matrix44.identity()

        if self.translation is not None:
            self.matrix = self.matrix * Matrix44.from_translation(self.translation)

        if self.rotation is not None:
            quat = quaternion.create(
                x=self.rotation[0],
                y=self.rotation[1],
                z=self.rotation[2],
                w=self.rotation[3],
            )
            self.matrix = self.matrix * Matrix44.from_quaternion(quat).transpose()

        if self.scale is not None:
            self.matrix = self.matrix * Matrix44.from_scale(self.scale)

    @property
    def has_children(self):
        return self.children is not None and len(self.children) > 0

    @property
    def is_resource_node(self):
        """Is this just a reference node to a resource?"""
        return self.camera is not None or self.mesh is not None


class GLTFMaterial:
    def __init__(self, data):
        self.name = data.get("name")
        # Defaults to true if not defined
        self.doubleSided = data.get("doubleSided") or True

        pbr = data["pbrMetallicRoughness"]
        self.baseColorFactor = pbr.get("baseColorFactor")
        self.baseColorTexture = pbr.get("baseColorTexture")
        self.metallicFactor = pbr.get("metallicFactor")
        self.emissiveFactor = data.get("emissiveFactor")


class GLTFImage:
    """
    Represent texture data.
    May be a file, embedded data or pointer to data in bufferview
    """

    def __init__(self, data):
        self.uri = data.get("uri")
        self.bufferViewId = data.get("bufferView")
        self.bufferView = None
        self.mimeType = data.get("mimeType")

    def load(self, path):
        # 

        # Image is stored in bufferView
        if self.bufferView is not None:
            image = Image.open(io.BytesIO(self.bufferView.read_raw()))
        # Image is embedded
        elif self.uri and self.uri.startswith("data:"):
            data = self.uri[self.uri.find(",") + 1:]
            image = Image.open(io.BytesIO(base64.b64decode(data)))
            logger.info("Loading embedded image")
        else:
            path = path / self.uri
            logger.info("Loading: %s", self.uri)
            image = Image.open(path)

        texture = t2d.Loader(
            TextureDescription(
                label="gltf", image=image, flip=False, mipmap=True, anisotropy=16.0,
            )
        ).load()

        return texture


class GLTFTexture:
    def __init__(self, data):
        self.sampler = data.get("sampler")
        self.source = data.get("source")


class GLTFSampler:
    def __init__(self, data):
        self.magFilter = data.get("magFilter")
        self.minFilter = data.get("minFilter")
        self.wrapS = data.get("wrapS")
        self.wrapT = data.get("wrapT")


class GLTFCamera:
    def __init__(self, data):
        self.data = data
        # "perspective": {
        #     "aspectRatio": 1.0,
        #     "yfov": 0.266482561826706,
        #     "zfar": 1000000.0,
        #     "znear": 0.04999999701976776
        # },
        # "type": "perspective"
